1. Field of the Invention
The present invention relates to circuitry for limiting power transients when printed circuit (PC) boards are plugged into a powered up system. More particularly, the present invention relates to such circuitry utilized with PC boards which plug into a telephone signal distribution bank.
2. Description of the Background Art
A signal distribution bank used by telephone companies includes shelves or slots on a backplane for connecting PC boards, the PC boards which plug in include "multiplexer" cards for switching signals provided to the distribution bank, and "distribution" cards, for transferring signals from the distribution bank to remote users or subscribers. With such signal distribution banks, telephone companies can start with only a few PC board slots occupied and later fill in the remainder. One such signal distribution bank is the Litespan.RTM. LS2012 manufactured by DSC Communications Corporation, Plano Tex.
With PC boards including circuitry to continually switch telephone signals after installation, it is not desirable to shut down a signal distribution bank to install additional PC boards. With the signal distribution bank powered up when a new PC board is installed, power transients can be created in the power supply of a backplane where the PC board is inserted. Such power transients can cause erroneous signals to be provided by sensitive analog components on PC boards already installed on the backplane.